Sung-Ku Ahn

Aperture maneuver with compelled breath (AMC) for moving tumors: A feasibility study with a moving phantom

Respiration causes target motion, which is known to be one of the technical bottlenecks in radiotherapy, especially for stereotactic radio-surgery and intensity modulated radiotherapy (IMRT). To overcome this problem, aperture maneuver with compelled breath (AMC) has been developed. In order to simulate compelled respiratory motion, a moving phantom using a ventilator was designed. As the air flow was forced to the bellows, which simulates the lungs, by a ventilator, a film connected to the ventilator moved like the respiratory target motion. A software was developed to transfer multileaf collimator motion from breathless to actual periodic breathing conditions. Static fields as well as step-and-shoot IMRT fields were modified in accordance with moving shapes to follow the target position, using the software with the controlled breathing information. Film dosimetry for a small field and for IMRT fields with a moving phantom was performed. To evaluate clinical implementation, five healthy volunteers were tested to breathe through a ventilator, and all of them could adapt the compelled breath without any difficulties. Additive margins for a moving target with AMC were not larger than 3 mm for respiratory organ motions up to 18 mm, while those with the static beam were 9 mm. For IMRT fields, large discrepancies were present between a static target and a moving target with the static beam, while they coincided well with AMC. Clinical acceptable differences between the dose distributions from a static target with the static beam and from a moving target with AMC revealed that this technique could be applied clinically.

Recombinant human epidermal growth factor treatment of radiation-induced severe oral mucositis in patients with head and neck malignancies

Mucositis of the oral cavity and pharynx is a major dose-limiting factor in the application of radiotherapy (RT) to patients with head and neck cancer. Therefore, we evaluated the wound healing effect of human recombinant epidermal growth factor (rhEGF) in head and neck cancer and lymphoma patients with irradiation (with or without combined chemotherapy-induced oral mucositis). Patients at Asan Medical Center who had undergone definitive RT of the head and neck region with or without combined chemotherapy and who had developed severe oral mucositis (higher than the Radiation Therapy Oncology Group grade 3) were treated with topical rhEGF twice daily for 7 days. The evaluation of response with regard to oral mucositis was performed 1 week later. Of the 11 treated patients, three had nasopharyngeal carcinoma, three had carcinoma of the oropharynx, two had carcinoma of the oral cavity, one had carcinoma of the hypopharynx and two had lymphoma of the head and neck. Six patients received RT only, and five patients received concurrent chemoradiotherapy. All patients showed improvements in their oral mucositis after topical treatment with rhEGF in that the Radiation Therapy Oncology Group grade was significantly decreased (P = 0.0000). This finding suggests that rhEGF is effective and safe for the treatment of radiation-induced mucositis. Further studies are needed to determine the optimal dosage and fractionation schedule.

Treatment results of post-operative radiotherapy in patients with salivary duct carcinoma of the major salivary glands

OBJECTIVEnSalivary duct carcinoma (SDC) is a rare malignancy of high-grade pathological type. We evaluated clinical outcomes and prognostic factors in 35 patients with SDC treated post-operatively with adjuvant radiation.nnnMETHODSnWe retrospectively assessed overall survival, locoregional control and disease-free survival in 35 patients with SDC of the major salivary glands who underwent surgery and were subsequently treated with radiotherapy. The evaluated prognostic factors included gender, age, symptom duration, tumour site, tumour size, TNM classification, and the following pathological features: perineural invasion, lymphovascular invasion, extraparenchymal invasion and resection-margin status.nnnRESULTSnOf the 35 patients, 30 (85.7%) were male. Median age at initial diagnosis was 62 years (range 38-75 years). The parotid gland was the main site affected in 22 patients (62.9%). 18 patients (51.5%) had pathological T3/T4 tumours, and 26 (74.3%) showed pathological nodal involvement. Actuarial 5-year locoregional control, disease-free survival and overall survival rates were 63.3%, 47.4% and 55.1%, respectively. The cause-specific death rate was 31.4% (n=11). Pathological nodal involvement was correlated with distant metastasis (p=0.011). Lymphovascular invasion was significantly prognostic for distant metastasis-free survival (p=0.049), locoregional control (p=0.012) and overall survival (p=0.003) in a Cox proportional hazard model, whereas perineural invasion was only significantly prognostic for overall survival (p=0.005).nnnCONCLUSIONSnSurgery and post-operative radiotherapy were effective for locoregional control. Lymphovascular invasion and perineural invasion were significant prognostic factors in patients with SDC.

Altered epidermal lipid layers induced by long‐term exposure to suberythemal‐dose ultraviolet

Backgroundu2002 Although several studies have reported on the biological effects of ultraviolet (UV) radiation, there have been only a few reports on the changes in epidermal lipids following long‐term UV irradiation at suberythemal dose (SED), to which people are usually exposed during their lifetime.

Predictive factors of bacteremia in patients with febrile urinary tract infection: an experience at a tertiary care center

PurposeTo investigate the clinical features in adult patients with febrile urinary tract infection (UTI) who visited the emergency department (ED) and to determine the predictive factors of bacteremia among the initial presenting clinical features.MethodsThis retrospective cohort study was conducted at the ED of a tertiary hospital in Korea from 1 January 2012 to 31 December 2012. All adult patients who were diagnosed with febrile UTI and for whom data on blood and urine cultures were available were included in the study. Clinical examinations and laboratory tests were performed at the initial presentation.ResultsA total of the 325 patients with febrile UTI (median age: 60 years) were included for analysis, of whom 82xa0% were female. Bacteremia was detected in 106 of the 325 patients (32.6xa0%), with Escherichia coli the most frequent pathogen detected (59.7xa0% of cases). Between the bacteremic and non-bacteremic groups, there was significant difference in age (67 vs. 57xa0years, respectively), flank pain (16 vs. 7.8xa0%), suprapubic discomfort (0 vs. 4.6xa0%), body temperature (38.8 vs. 38.3xa0°C), respiratory rate (21 vs. 20/min), platelet count (170 vs. 186xa0×xa0103/μL), C-reactive protein (10.2 vs. 8.3xa0mg/dL), and procalcitonin (1.5 vs. 0.3xa0ng/mL) (Pxa0<xa00.05 for all). In the multivariate logistic regression analysis, age [odds ratio (OR) 1.03; 95xa0% confidence interval (CI) 1.01–1.05], systolic blood pressure of <90xa0mmHg (OR 3.27; 95xa0% CI 1.13–9.45), body temperature of >39xa0°C (OR 4.26; 95xa0% CI 2.28–7.96), and procalcitonin level of >0.5xa0ng/dL (OR 2.03; 95xa0% CI 1.07–3.86) were significantly associated with bacteremia.ConclusionAmong our adult patients with febrile UTI, age, systolic blood pressure, body temperature, and procalcitonin were significantly associated with bacteremia. We therefore suggest that these factors should be considered when deciding upon treatment options for febrile UTI patients at the ED.

Stage IE/IIE extranodal NK/T-cell lymphoma arising in the nasal cavity: analysis of CT findings and their prognostic value.

AIMnTo investigate the computed tomography (CT) findings in patients with stage IE/IIE extranodal natural killer/T-cell lymphoma (ENKTL) arising in the nasal cavity and to evaluate whether imaging findings revealed by CT have prognostic value.nnnMATERIALS AND METHODSnThe CT findings of 62 patients diagnosed with IE/IIE ENKTL arising in the nasal cavity were retrospectively reviewed. Imaging findings were investigated, and evaluated imaging findings were analysed for the prognostic value of overall survival (OS) and disease-free survival (DFS).nnnRESULTSnOf the 62 patients, 21 (34%) presented with a superficial infiltrative, 38 (61%) with a mass forming, and three (5%) with a combined pattern. Of all imaging findings, local invasiveness (n = 26, 42%), including bony destruction, erosion, or soft-tissue involvement, was the only independent prognostic factor for OS [p = 0.008; hazard ratio (HR): 3.85; 95% confidence intervals (CI): 1.42-10.44] and DFS (p = 0.001; HR: 4.25; 95% CI: 1.72-10.47). In a subgroup analysis of 36 cases with no local invasiveness, a superficial infiltrative pattern in one nasal cavity was a positive prognostic factor for OS (p = 0.028) and DFS (p = 0.008).nnnCONCLUSIONnImaging findings at CT provided clinically useful predictions for treatment outcomes. Local invasiveness revealed by CT findings was a strong prognostic factor for poor OS and DFS. In addition, in patients with no local invasiveness, a superficial infiltrative pattern in one nasal cavity predicted favourable OS and DFS.

SU‐FF‐T‐477: Study On the Modeling of Digital Couch for Proton Treatment Planning System

Purpose: To evaluate the modeling of couch with a commercial protontreatment planning system (TPS, Eclipse, v8.12). Method and Materials: To keep the shape and dimensions of an actual proton treatment couch, it was scanned using CT scanner and inserted into the TPS system by replacing CT couch of all transverse CT slices. Results: The experimental data shows that the range of proton beam is shorten by 0.99 ± 0.01cm and spread‐out Bragg peak (SOBP) varies 0.10 ±0.09cm with insertion of proton couch when the beam direction is perpendicular to proton couch (0° in our configuration). While the average range shift in proton beam increases from 0.99cm to 1.70cm as the angle of the beam increases from 0° to 55°, there were no distinct SOBP changes with beam angle revealing less than 0.1cm variation. Our results suggest that the dosimetic factors such as range, profile, output factor remained almost same with the insertion of proton couch, whereas the beam range is largely dependent on both the insertion of couch and beam angle to couch. Using inserted CT scanned proton couch in TPS, the calculated and measured beam range was cross‐compared and the results show that the range of proton beam is shorten by ∼0.7cm in TPS, which shows ∼0.3cm difference with actual measurement. The difference between computed and measured range was compensated by assigning appropriate densities to the inserted proton couch, which is called digital couch. Measured and computed PDD with the digital couch show that the beam range and SOBP are well matched for various beam angles revealing the difference of 0.01±0.02cm and 0.12±0.03cm, respetively. Conclusion: These results suggest that the digital couch with relevant density assignment may be a good solution for proton couch modeling, which can be used for commercial proton TPS.

SU‐FF‐T‐181: The Development of Eye Treatment Gating System for the Proton Therapy

Purpose:Proton therapy is suggested as a next generation radiation therapy with their great dose localization performance compared with linear accelerator. Although proton therapy is recommended for eye melanoma treatment due to its excellence in dose localization, the patient positioning system (PPS) is essential since small error in PPS may cause significant damage to the patient. In this study, we developed an automatic real time eyeball tracking and gating system for the treatment of eye melanoma Method and Materials: A gating system was developed using Labview 8.6 software with GUI based development tool (National Instrument). The real time image for eye movement was taken using CCDcamera, which was transferred to the homemade image analysis program. Using the eye gating system, a real time eye ball tracking based on image pattern matching method was realized by comparing a treatment template image used in the treatment planning with a real time image acquired from CCDcamera. And generating the gating control TTL trigger signal for the proton beam on and beam off . Results: Based on the real time image analysis system, we achieved the real time eye ball tracking system with a resolution less than 0.01mm for the eye ball movement which will be used for the treatment of ocular tumor in proton therapy, We can controlled the proton beam on and beam off with a time delay less than 0.1 sec for the eye movement to over range for tolerance value. Conclusion:. We have developed eye movement gating system for eye treatmentproton therapy at our facility. The system will be use for eye movement gated treatment for ocular patient. This study was supported by the Korean Ministry of Health and Welfare, Republic of Korea (A080345), Key words: Eye gating system, Proton therapy, Ocular, Eye treatment,

SU-E-T-178: Clinical Feasibility of Multi-Leaf Collimator Based Dynamic Wedge

Purpose: A multi-leaf collimator (MLC) based dynamic wedge (MDW), which provide similar dose profile of physical wedge (PW) along x-jaw direction while significant monitor unit (MU) reduction, was developed and investigated for clinical use. Methods: A novel technique was used to create the wedge profile using MLC. A modification was applied to the DICOM-RT format file of the plan made with the PW to replace PW with MDW. The Varian enhanced dynamic wedge profile was used to produce MLC sequence, while the MU of the wedged field was recalculated using PW factor and fluence map. The profiles for all possible MDWs to substitute PWs were verified in 6/15 MV x-ray irradiations. New plans with MDWs were compared with the original plans in 5 rectal, 5 RT breast and 5 liver cases. Results: The wedge profile of the MDW fields were well matched with those of PWs inside the fields while less scatter than PW out of the fields. For plan comparisons of the clinical cases no significant dose discrepancy was observed between MDW plan and PW’s with the dose volume histograms. The maximum and mean doses in PTVs are agreed within 1.0%. The Result of OARs of MDW plans are slightly improved in the maximum doses (3.22 ∼ 150.4 cGy) and the mean doses (17.18 ∼ 85.52 cGy) on average for all cases while the prescribed doses are 45 Gy for rectal cases, 40 or 45 Gy for liver cases and 50 Gy for breast cases. The MUs of the fields which replace PW with MDW are reduced to 68% of those of PW. Conclusion: We developed a novel dynamic wedge technique with MLC that shows clinical advantage compared to PW.

SU-E-T-269: Quality Assurance of Spine Volumetric Modulated Arc Therapy with Flattening Filter Free Beams Using Gafchromic EBT3 Films

PURPOSEnWe implemented the Gafchromic film-based patient specific QA of volumetric modulated arc therapy (VMAT) with flattening-filter free (FFF) beams for spine metastases and validated the accuracy of fast arc delivery.nnnMETHODSnEBT3 films and a homemade cylindrical QA phantom were employed for dosimetric verification of VMATs. For 14 FFF VMAT plans (10 with 10-MV FFF beams and 4 with 6-MV FFF beams), the doses were recalculated on the phantom and delivered by a TrueBeam STx accelerator equipped with a high-definition 120 leaf MLC. The EBT3 films were scanned using an Epson 10000XL scanner through the FilmQA Pro software. All the irradiated film images were converted to dose map using a calibration response curve. The resulting dose map of film measurement was compared with treatment plan and evaluated using gamma analysis with dose tolerance of 2% within 2 mm. In addition, the point-dose measurement in the phantom using an ion chamber was evaluated as a reference in a ratio of measured and planned doses.nnnRESULTSnThe gamma pass rates averaged over all FFF plans for composite-field measurements were 96.0 ± 3.6% (88.9%-99.5%). When adopting a tolerance level of 3% - 3 mm, the gamma pass rates were improved with the ranges from 98% to 100%. In addition, dose profiles and dose distributions showed that spinal cord was protected by the rapid dose fall-off and by delivering the treatment with high precision. In point-dose measurements, the average differences between the measured and planned doses were 0.5% ± 1.0% of the prescription dose.nnnCONCLUSIONnWe demonstrated that Gafchromic EBT3 film would be an effective patient-specific QA tool, especially for VMAT of spine SBRT with treatment of small fields and highly gradient dose distributions. The results of film QA verified that the dosimetric accuracy of spine SBRT utilizing RapidArc with FFF beams in our institution is reliable.